Vacuum-pump.



W. GAEDE.

VACUUM PUMP.

APPLICATION FILED APR. 8, 1914.

Patented May 4, 1915.

INVENTEI R WITNESSES wonmane canon, or ammo, an n VAC-1.

speclfication'of Letters Patent.

rammed May a, 1915.

Application filed April 8, 1914. Serial No. 880,347.

To all whom it may concern:

Be it known that I, WOLFGANG GAEDE, a subject of the Emperor of Germany, residing at No. Badenia, Germany, have invented certain new and useful Improvements in Vacuum- Pumps; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to vacuum pumps of the piston type capable of producing a high degree of vacuum and having a distributing valve actuated in constant phase relation to the stroke of the ump. In prior pumps of this kind, the plston is brought into substantial contact with the cylinder head in order to decrease the dead space from which the air or gas is exhausted from the cylinder during each stroke, but they employ a positively actuated distributing valve of the klnd in which a comparatively large dead space exists in the passage between the interior of the cylinder and the valve, tenuation obtained at each stroke. This condition may be improved by introducing a liquid for filling the dead space during each stroke of the piston, but then the va or of the filling liquid passes into the cylin er, while the filling liquid absorbs the gas be-. ing exhausted and returns it into the vacuum chamber. The type of pump disclosed herein does not employ a filling liquid, but the dead space is filled with a solid part when the piston is at rest in substantial contact with the cylinder head, whereby the gas is discharged in its substantial entirety at each discharge stroke of the pump. In the specific embodiments shown herein, the piston rod is connected in limited sliding engagement with the piston, so that there is suflicient relative movement between the two upon reversal of reciprocation to brlng about the desired operation of the pump in this way.

In the accompanying dlagrammatic drawings, Figure 1 represents a view, principally in central vertical section, of a two stage pump showing one modification within my invention and Fig. 2 represents a fragmentary view, principally. in central vertlcal 'section, showing: another modification within my invention.

Referring particularly to Flg. 1, the in- 8 Schwarzwaldstrasse, Freiburg,

and thus decreases the degree of at-- contact with the piston terior of the work cylinder A is communication through the opening 0 with the space to be exhausted to a high degree of vacuum. The second stage cylinder B is arranged. in axial alinement with the work cylinder, and is in communication therewith through the outlet E in the end wall C of the work cylinder, this end wall forming a partition between the twocylinders. A s1ngle piston rod serves for reciprocating the work piston G and the second stage piston L, the latter being fastened tightly on the larger portion D thereof, and the work piston being connected in sliding engagement therewith on the reduced portion F. The piston L is provided with a passage containing the relief valve M, and the end wall of the second stage cylinder is provided with a similar valved passage N. The stroke of the piston rod is such that the work piston G is moved to an extreme position in substantial contact with the end wall C at the end of the pressure or discharge stroke, while the piston L is simultaneously brought near the outer end of its cylinder. The-portion F of reduced section of the piston rod is slidable with a substantially gas tight fit through the piston G, and the portion D of larger section is slidable through the outlet E with a substantially gas tight fit, its lower end being slightly beveled. During the upward stroke, the work piston G is moved from the bottom of the cylinder A and from beyond the opening 0 toward the end wall C of the work cylinder. The portion D' of larger section maintains the outlet E closed until the piston G is nearing the end wall C, whereupon, as represented in Fig. 1, the portion F of reduced section enters the outlet E and establishes communication to the second stage cylinder from that part of the work cylinder which lies between the piston G and the end wall C.

At the extreme end of the stroke the us-- ton is brought into substantial contact with the end wall C, as is indicated in this respect in Fig. 2. The piston G remains at rest in this position until the lower end of the larger portion D of the piston rod has, after reversal of ,its reciprocation, come into G. As a result of the upper conical portion of the outlet IE, only that gas which is in the thin annular space between the beveled portion of the piston rod and the side wall of the cylindrical portion of the outlet E, is trapped between the end of the larger portion nor the piston rod and the upper surface of the piston G; The piston will then be moved on its downward stroke to the other end of the work cylinder beyond the opening 0, to be exhausted will expand into the work cylinder A. The gas which is trapped in [the cylinder will at first becompressed during the upward stroke of'the work piston G and will ultimately be.discharged through the outlet E into the second stage cylinder B. This gas will then be trapped in the cylinder B, and will be discharged therefrom through the relief valve M on the downward stroke of the piston L and will finally be discharged from this space into the atmosphere, or other place, through the relief valve N whenthe piston L is nearing the end of its upward stroke. In this way, the pressure tending to return the gas through the outlet E is reduced so that the leakage back into the work cylinder may be made very small. In addition to this action, the cylinder B performs another important function, as a result of the fact that the piston L is moved into substantial contact with the partition 0 at the end of the outward stroke. Lubricating oil running down the cylinder reaches the upper surface of the partition C and would then pass into the work cylinder when the outlet E was opened, and finally into the Vacuum below the piston G, unless provision is made for removing this oil during each stroke before the outlet E is opened. By the arrangement herein shown, the oil which reaches the top surface of the partitionC is forced through the relief valve M. when the piston L comes into substantial contact with this surface, and it is therefore removed before it has a chance to get into the work cylinder.

The arrangement of Fig. 2 is similar in construction and operation to that of Fig. 1, except that the outlet E from the work cylinder A is filled by a plug valve H slidably mounted with a substantially gas tight fit on the portion D of the piston rod. This valve is opened near the end of the pressure.

stroke of the work piston G by means of the shoulder at the junction of the reduced section D andenlarged section F of the piston rod. The flat spring K assists gravity in forcing the plug H down into its conical seat. The pin and slot connection I between the piston G and the enlarged portion F of the piston rod provides sliding engagement of limited extent between the two of a gas tight nature, so that'the outlet E is opened as the work piston G is nearing the end of the pressure stroke, and is filled while the piston G is at rest in substantial contact with the end wall C. The plug H is designed to conform to the top surface of the partition whereupon the gas in the space E ultimately 0 when the plug is seated, and hence the lubricating oil may be most eifectively prevented from entering the work cylinder by such an arrangement as is shown in Fig. 1.

It will be observed in both Figs. 1 and 2, that there is substantially no dead space to reduce the effectiveness of the pump and the degree of vacuum which can be attained. Furthermore, the outlet E is substantially filled, and therefore contains practically no dead space, before the work piston G is, moved away from its extreme position in substantial contact with the end wall of the cylinder. 1

Having thus describedmy invention what I-claim is: v

1. In a vacuum pump, the combination with a cylinder having an outlet, a piston reciprocative in the cylinder, and a piston rod designed to move the .piston intoand away from an extreme position of substantial contact with the end wall of the cylinder, of means positively actuated by a reciprocative part for substantially filling said outlet when the piston is at rest in said extreme position; substantially as described.

2. In a vacuum with a cylinder having an outlet, a piston reciprocative in the cylinder, and a piston rod designed to move thepiston into and away from substantial contact with an end wall of the cylinder, of means for establishing an outlet through said wall when the piston is nearing'said Wall and for substantially filling said outlet when the piston is at rest in substantial contact with said wall; substantially as described.

In a vacuum pump, the combination with a cylinder having an opening for communication with the space to be exhausted and also having an outlet, a piston reciprocative in the cylinder, and a piston rod designed to move the piston beyond said opening on its downward stroke and also into'an extreme position of substantial contact with the inner end Wall of the cylinder on its upward stroke, of means positively actuated by a reciprocative part for substantially filling said outlet when the piston is at rest in said extreme position and for maintaining said outlet substantially filled until the piston has passed said opening on its-upward.

stroke; substantially as described.

In a vacuum pump, the combination of a cylindenhaving an outlet, a piston reciprocative in the cylinder, a piston rod having a limited sliding engagement with the piston, means for opening said outlet when the piston is near g the end of its discharge stroke, and means operative during the sliding engagement between the piston rod and the piston for closing the outlet when the piston is at rest at the end of the discharge stroke; substantially as described.

pump, the combination 5. In a vacuum pump, the combination of a cylinder having an outlet in the .end wall, a piston reciprocative in the cylinder, and a piston rod having a limited sliding engagement with the piston and being designed to move the piston into and away from an extreme position in substantial contact with the end wall, said piston rod passing through said outlet and having means for opening said outlet when the piston is nearing said extreme position and for closing said outlet when the piston is in said extreme position; substantially as described.

6. In a vacuum pump, the combination of a cylinder having an outlet in its end wall, a piston reciprocative in the cylinder, and a piston rod passing through said outlet and having a portion of reducedsection in lim-. ited sliding engagement with the piston to move it into and away from an extreme position of substantial contact with said end wall,the arrangement being such that the reduced portion of the piston rod enters the outlet when the piston is. nearing said extreme position to thereby establish communication through the outlet during the end of the discharge stroke and also so that the portion of larger section of the piston rod enters the outlet before the piston is moved away from said extreme position to thereby close said outletfrom the beginning of the next stroke; substantially as described.

der, said piston rod being connected lim- 1ted sliding engagement with the piston of vthe Work cylinder and being efiective to first establish communicationthrough said passage and to then interrupt said cbmmunication when the piston of the work cylinder is at rest at one end of the stroke; substantially as described.

8. In a vacuum pump, the combination of a work cylinder having an opening for-communication with the space to be exhausted,

a second stagecylinder in axial alinement with the work cylinder, a passage arranged in the partition between the cylinders, an individual piston in each cylinder, a piston rod passing through said passage and being designed to reciprocate the piston in the work cylinder to an extreme position in substantial contact with the end wall, a relief valve in the piston ofthe second stage cylinder, and a relief valve in the end wall of the second stage cylinder, said piston rod having a reduced portion connected in limited sliding engagement with the piston of the work cylinder so as to maintain the passage between the cylinders closed by its larger section from the beginning ofthe i downward stroke from said extreme position until the piston is nearing. said extreme position in the upward stroke, and again closing said passage when the piston of the work cylinder is at rest'in said extreme position; substantially as described. p

In testimony whereof I afix my signature in presence of two witnesses.

/ wonreane earns. 

